yamaha 80 prob

[sambo165]

hi i have a 2005 yam 80 hp 4 stroke around 400hrs .which im havin trouble with.
turn key and engine somtimes hesatates to start then it may start.
1100 revs then tries to idle but starts to run rough and then stops.
if i give it some trottle it wont try to fire at all .
when i get it started without trottle it most time starts then i try to rev up to keep it goin it stops.
tried all fuel related issuses .
bit we think it may be an electrical issue sensor or ecu prob.
can anyone help on this were really stuck and the nearest dealer with diagnostics is 250 mile away and as im not getting and managment light flashing on the tacho which i thought i may if it was a sensor .
thanks

[sambo165]

a bit of an update.
so i decided to remove the vst as mecanhic said he douths it has anything to do with my prob.
didnt seem to be any dirt in there but i gave it a blow out anyhow,
then i connected a battery to the pump and it ran .
so i put it all back together and tried the engine turned over a few times and all of a sudden it started.
it now seems tom start and rev up fine.
im goin to bring it out for a run later to see what happens.
could it just of been that it was blocked were the petrol enters the vst os somthing.

[sambo165]

so i brought the boat out and it started and ran great.
was out for 2 hours running th engine hard ang *****ing and it seems fine.
the only prob i seem to have is i forgot to turn the battery isolator off and i went out today and the battery was dead. key was turned off in ignision and all electronics were off .
could the engine drain the battery when turn off.

[hewesbayfisher90hp]

Thoughts

Some things run even when the switch is turned off - just depends on how it is wired, if someone did some modifications to something - so the best and only way is to turn it off at the main battery isolate switch. Take a reading on the output of the switch, and make sure you are not reading anything when in the off position.